The present invention relates to a positive (type) photoresist composition used for the production of semiconductor integrated circuit elements, mask for producing integrated circuits, printed wiring boards and liquid crystal panels.
As pattern forming methods for producing electronic parts such as semiconductor elements (i.e., semiconductor device) magnetic bubble memories and integrated circuits, methods utilizing photoresists sensitive to ultraviolet rays or visible rays have hitherto been widely made practicable. The photoresists include negative type photoresists in which irradiated portions are insolubilized in developing solutions by light irradiation, and positive type photoresists in which irradiated portions are conversely solubilized in developing solutions. The negative type photoresists are higher in sensitivity than the positive ones, and excellent in adhesion with substrates and chemical resistance which are required for wet etching, so that the negative type photoresists have occupied the main stream of photoresists until recently.
However, with increased density and integration of semiconductor elements, the line width and the distance have become extremely small, and dry etching has come to be employed for etching of substrates. Accordingly, high resolution and high dry etching resistance have become to be desired for photoresists. At present, the photoresists have been mostly occupied by the positive type photoresists. Of the positive type photoresists, for example, alkali development type positive photoresists based on alkali-soluble novolak resins described in J. C. Strieter, Kodak Microelectronics Seminar Proceedings, 116 (1976) have been mainly used in the current processes, because of their excellent sensitivity, resolution and dry etching resistance.
However, with recent multifunctionalization and advancement of electronic equipments, it has been strongly demanded that patterns are made fine for further increasing the density and the integration.
That is to say, the longitudinal dimension of integrated circuits has not been decreased so much, compared with a reduction in the transverse dimension thereof, so that the ratio of the height to the width of resist patterns can not help increasing. For this reason, with advance of making patterns fine, it has become more difficult to suppress changes in the size of resist patterns on wafers having complicated differences in level.
Further, also in various kinds of exposure systems, problems have arisen, associated with a reduction in the minimum dimension. For example, in light-exposure, the interference action of reflected light based on the differences in level of substrates has exerted a great influence on the dimensional accuracy, whereas in electron beam-exposure, the proximity effect generated by the back scattering of electrons have made it impossible to increase the ratio of the height to the width of the fine resist patterns.
It has been found that these many problems are solved by the use of the multilayer resist system. As to the multilayer resist systems, the outline thereof is given in Solid State Technology, 74 (1981). In addition to this, many studies of this system have been presented.
In general, the multilayer resist methods include a three-layer resist method and a two-layer resist method. The three-layer method is a method of forming a flattened organic film on a substrate having differences in level, overlaying an intermediate inorganic layer and a resist thereon, patterning the resist, then dry etching the intermediate inorganic layer using the patterned resist as a mask, and further patterning the flattened organic film using the intermediate inorganic layer as a mask by O2RIE (reactive ion etching). In this method, basically, conventional techniques can be used, so that studies have been initiated early. However, the problem is encountered that the process is very complicated, or that three layers of the organic layer, the inorganic layer and the organic layer different from one another in properties are overlaid with one another, so that cracks and pin holes are liable to generate in the intermediate layer.
In contrast with the three-layer resist method, the two-layer resist method uses a resist combining properties of both the resist and the intermediate inorganic layer used in the three-layer resist method, that is to say, a resist having oxygen plasma resistance. Accordingly, the generation of cracks and pinholes is inhibited, and the process is simplified from three layers to two layers. However, although a conventional resist can be used as the upper-layer resist in the three-layer resist method, the two-layer resist method has the problem that a resist having oxygen plasma resistance must be newly developed.
From the above-described background, the development of positive type photoresists being able to be used as the upper-layer resist in the two-layer resist method, excellent in oxygen plasma resistance, and high in sensitivity and resolution, particularly resists of the alkali development system which can be used without changing the present process has been desired.
In contrast, there are proposed light-sensitive compositions in which alkali solubility-imparted polysiloxanes or silicone polymers such as polysilylmethylene are combined with conventional orthoquinonediazide light-sensitive materials, for example, light-sensitive compositions described in JP-A-61-144639 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d, JP-A-61-256347, JP-A-62-159141, JP-A-62-191849, JP-A-62-220949, JP-A-62-229136, JP-A-63-90534, JP-A-63-91654 and U.S. Pat. No. 4,722,881, and further light-sensitive compositions described in JP-A-62-136638, in which effective amounts of onium compounds are combined with polysiloxane/carbonate block copolymers.
However, to any of these silicone polymers, the alkali solubility is given by introduction of phenolic OH groups or silanol groups (xe2x89xa1Sixe2x80x94OH). When the alkali solubility is given by introduction of phenolic OH groups, the production thereof becomes significantly difficult. When the alkali solubility is given by introduction of silanol groups, there is the problem that the aging stability is not necessarily good, or that the film reduction after development is increased, resulting in failure to obtain rectangularity.
Further, Japanese Patent No. 2736939 and JP-A-9-274319 disclose photoresists containing polysiloxanes having groups decomposable by the action of acids in their molecules. However, these photoresists have the problems that the resolution is low, that rectangularity is not obtained, and that the dimension shift of pattern is increased in pattern transfer to the lower layers in the subsequent oxygen plasma process.
An object of the present invention is to provide a positive type photoresist composition high in sensitivity in the production of a semiconductor device, having a resolution as high as 0.2 xcexcm or less, and giving a photoresist pattern having rectangularity.
Another object of the present invention is to provide a positive type photoresist composition decreased in dimension shift of pattern in pattern transfer to the lower layer in the oxygen plasma etching process, when it is used as an upper-layer resist in the two-layer resist system.
A further object of the present invention is to provide a polysiloxane which can give the above-described excellent characteristics to a positive type photoresist composition.
According to the present invention, the following polysiloxane and positive type photoresist composition are provided, thereby attaining the above-described objects of the present invention:
(1) A positive (type) photoresist composition comprising an alkali-soluble or acid-decomposable polysiloxane containing repeating structural units represented by formula 
xe2x80x83wherein L represents at least one divalent connecting group selected from the group consisting of xe2x80x94Axe2x80x94NHCOxe2x80x94, xe2x80x94Axe2x80x94NHCOOxe2x80x94 and xe2x80x94Axe2x80x94NHCONHxe2x80x94, wherein A represents a single bond, an alkylene group or an arylene group; X represents a single bond or a divalent connecting group; and Z represents either a group represented by 
or a group represented by 
wherein Y represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, an atomic group represented by Y may be straight-chain, branched or cyclic, R represents a hydrogen atom or an acid-decomposable group, 1 represents an integer of from 1 to 3, and m also represents an integer of from 1 to 3;
(2) The positive (type) photoresist composition described in (1), which comprises an alkali-soluble or acid-decomposable polysiloxane further containing repeating structural units represented by formula (II) together with the units represented by formula (I): 
xe2x80x83wherein Axe2x80x2, Xxe2x80x2 and Zxe2x80x2 each has the same meaning as given for each of A, X and Z in formula (I);
(3) The positive (type) photoresist composition described in (1), which comprises an alkali-soluble polysiloxane wherein R contained in the group represented by Z in formula (I) is a hydrogen atom;
(4) The positive (type) photoresist composition described in (2), which comprises an alkali-soluble polysiloxane wherein R contained in the group represented by Zxe2x80x2 in formula (II) is a hydrogen atom;
(5) The positive (type) photoresist composition described in (2), wherein Axe2x80x2 is xe2x80x94(CH2)nxe2x80x94 in formula (II);
(6) The positive (type) photoresist composition described in (1), wherein L is xe2x80x94(CH2)3xe2x80x94NHCOxe2x80x94 in formula (I);
(7) The positive (type) photoresist composition described in (3), which further contains a phenolic compound in which at least a part of phenolic hydroxyl groups contained in a molecule are partially or completely protected by acid-decomposable groups;
(8) The positive (type) photoresist composition described in (3), which further contains an aromatic or aliphatic carboxylic acid compound in which at least a part of carboxyl groups contained in a molecule are partially or completely protected by acid-decomposable groups;
(9) A positive (type) photoresist composition comprising the following (a), (b), (c) and (d):
(a) an alkali-soluble or acid-decomposable polysiloxane containing repeating structural units represented by formula (I): 
xe2x80x83wherein L represents at least one divalent connecting group selected from the group consisting of xe2x80x94Axe2x80x94NHCOxe2x80x94, xe2x80x94Axe2x80x94NHCOOxe2x80x94 and xe2x80x94Axe2x80x94NHCONHxe2x80x94, wherein A represents a single bond, an alkylene group or an arylene group; X represents a single bond or a divalent connecting group; and Z represents either a group represented by 
or a group represented by 
wherein Y represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, an atomic group represented by Y may be straight-chain, branched or cyclic, R represents a hydrogen atom or an acid-decomposable group, 1 represents an integer of from 1 to 3, and m also represents an integer of from 1 to 3;
(b) a compound which is decomposed by exposure to generate an acid;
(c) (c1) a phenolic compound in which at least a part of phenolic hydroxyl groups contained in a molecule are partially or completely protected by acid-decomposable groups, or
(c2) an aromatic or aliphatic carboxylic acid compound in which at least a part of carboxyl groups contained in a molecule are partially or completely protected by acid-decomposable groups; and
(d) a solvent which can dissolve all of the above (a), (b) and (c);
(10) The positive (type) photoresist composition described in (9), which comprises an alkali-soluble or acid-decomposable polysiloxane further containing repeating structural units represented by formula (II) together with the units represented by formula (I): 
xe2x80x83wherein Axe2x80x2, Xxe2x80x2 and Zxe2x80x2 each has the same meaning as given for each of A, X and Z in formula (I);
(11) The positive (type) photoresist composition described in (10), wherein Axe2x80x2 is xe2x80x94(CH2)nxe2x80x94 in formula (II);
(12) The positive (type) photoresist composition described in (9), wherein L is xe2x80x94(CH2)3xe2x80x94NHCOxe2x80x94 in formula (I);
(13) A positive (type) photoresist composition comprising the following (a), (b) and (d):
(a) an alkali-soluble or acid-decomposable polysiloxane containing repeating structural units represented by formula (I): 
xe2x80x83wherein L represents at least one divalent connecting group selected from the group consisting of xe2x80x94Axe2x80x94NHCOxe2x80x94, xe2x80x94Axe2x80x94NHCOOxe2x80x94 and xe2x80x94Axe2x80x94NHCONHxe2x80x94, wherein A represents a single bond, an alkylene group or an arylene group; X represents a single bond or a divalent connecting group; and Z represents either a group represented by 
or a group represented by 
wherein Y represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, an atomic group represented by Y may be straight-chain, branched or cyclic, R represents a hydrogen atom or an acid-decomposable group, provided that at least a part of repeating units in the polysiloxane is a repeating unit in which R is an acid-decomposable group, 1 represents an integer of from 1 to 3, and m also represents an integer of from 1 to 3;
(b) a compound which is decomposed by exposure to generate an acid; and
(d) a solvent which can dissolve both of the above (a) and (b);
(14) The positive (type) photoresist composition described in (13), which comprises an acid-decomposable polysiloxane further containing repeating structural units represented by formula (II) together with the units represented by formula (I): 
xe2x80x83wherein Axe2x80x2, Xxe2x80x2 and Zxe2x80x2 each has the same meaning as given for each of A, X and Z in formula (I);
(15) The positive type photoresist composition described in (14), wherein Axe2x80x2 is xe2x80x94(CH2)nxe2x80x94 in formula (II); and
(16) The positive type photoresist composition described in (13), wherein L is xe2x80x94(CH2)3xe2x80x94NHCOxe2x80x94 in formula (I).